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Runs rough only when cold

I have a 2001 Miata, with 61k on it. When I first start the car it runs rough. The RPM surges between 1100 and 1700 for abut a minute or 2 then smooths out to around 1100. If I give it some throttle, it will miss, with the frequency declining as it warms up. Once it reaches normal operating temperature it runs fine,idles at around 800, and I can pull a long hill at 4500+ RPM with no hesitation. I’ve replaced the fuel and air filters, as well as plugs and wires. I’ve have also replaced the intake air and coolant temp sensors, and cleaned the MAF sensor as well, and have now run 4 tankfuls of Chevron supreme with an added bottle of injector cleaner. There are no codes. I previously had a problem and replaced the cam position sensor. Any advice would be appreciated. Thanks- John